1. Field of the Invention
The present invention relates to a display apparatus in which display elements and a driving circuit are formed on the same insulating substrate, an image control semiconductor device, and a method for driving the display apparatus.
2. Related Background Art
A display apparatus in which a large number of display elements were arranged laterally and longitudinally on an insulating substrate has been known. As a representative example, there is a liquid crystal display apparatus.
In this kind of conventional display apparatus, separately from a pixel array substrate on which the display elements are arranged laterally and longitudinally, a driving circuit substrate is generally provided. For example, active matrix type display elements are formed near respective points of intersection of signal lines and scanning lines arranged laterally and longitudinally on the pixel array substrate. In addition, on the pixel array substrate, a signal line driving circuit for driving the signal lines and a scanning line driving circuit for driving the scanning lines are formed.
On the other hand, on the driving circuit substrate, agraphic controller IC for performing image processes such as development to a bit map and the like in accordance with an instruction from a CPU, and an LCD controller IC for performing rearrangement of the pixel data outputted from the graphic controller in accordance with structure and drive of the pixel array substrate and generating a signal to control peripheral circuits of the pixel array substrate and the display apparatus are formed. The LCD controller IC is constructed by a gate array or the like.
FIG. 36 is a block diagram of a conventional liquid crystal display apparatus and shows a case in which a pixel array portion 109 and a part of driving circuits (signal line driving circuit, scanning line driving circuit, and the like) are formed on a glass substrate by using polysilicon TFT's, and a CPU 100, a graphic controller IC 101, and a gate array (G/A) 102 are formed on the other substrate.
Referring to FIG. 36, the gate array 102 rearranges digital pixel data outputted from the graphic controller IC 101 and controls the peripheral circuits of the pixel array substrate and the display apparatus. An output of the gate array 102 is inputted to a D/A converter (DAC) 106 through a control circuit 103, a sampling circuit 104, and a latch circuit 105. The D/A converter 106 converts the digital pixel data into an analog voltage. After the analog voltage is amplified by an amplifier (AMP) 107, the voltage is selected by a selecting circuit 108 and is supplied to each signal line 109.
To realize a reduction in part costs and a miniaturization, it is necessary to reduce the number of parts, substrate area, and number of substrates. In the conventional display apparatus, since the driving circuit is constructed by using a plurality of circuits such as graphic controller IC 101, gate array 102, signal line driving circuit, and scanning line driving circuit, there is such a problem that the scale of the driving circuit cannot be reduced.
Recently, in the liquid crystal display apparatus, a technique of forming polysilicon TFT's (Thin Film Transistors), which can be operated at a high operating speed, on the glass substrate and forming not only the pixel array portion but also a part of the driving circuit on the glass substrate is advancing.
Though the polysilicon TFT can be operated at a high speed, however, the mobility is not so high. When the resolution is raised to shorten a cycle per pixel, the polysilicon TFT does not operate stably. Accordingly, hitherto, the graphic controller IC 101 and similar components, to which the high-speed operation is required, are generally provided on the outside of the glass substrate. The whole driving circuit cannot be formed so as to be integrated with the pixel array portion.
In the conventional liquid crystal display apparatus, data buses are arranged on the glass substrate. As the number of signal lines is larger in association with the large area of the glass substrate, the load capacity of the data bus is increased. When the load capacity of the data bus is increased, such a problem that the waveform becomes dull occurs. Accordingly, hitherto, the voltage amplitude of data to be transmitted through the data bus is increased. However, when the voltage amplitude of data to be transmitted through the data bus is increased, there is such a problem that power consumption is increased.